A chopper amplifier, also known as a chopper-stabilized amplifier or auto-zeroing amplifier, is a type of operational amplifier (op-amp) configuration designed to reduce offset voltage and offset drift. Offset voltage refers to the small voltage that appears at the output of an op-amp when the input terminals have zero differential voltage (meaning the same voltage is applied to both inputs).
Conventional op-amps have inherent imperfections in their fabrication that lead to offset voltage. This can cause inaccuracies and errors in precision applications where small signals need to be accurately amplified, such as in instrumentation, data acquisition systems, and sensor interfacing.
A chopper amplifier employs a technique called "chopping" or "auto-zeroing" to compensate for the offset voltage. The basic principle behind chopper amplifiers involves periodically switching the input and feedback paths of the amplifier between two or more different configurations. During one phase of the cycle, the amplifier measures the offset error and stores it temporarily. During the subsequent phase, the stored error is then used to cancel out the offset in the actual signal path.
The chopper technique effectively mitigates the impact of offset voltage by periodically recalibrating the amplifier, resulting in significantly reduced offset voltage and drift over time and temperature variations. As a consequence, chopper amplifiers are capable of achieving very high levels of DC precision and accuracy, making them suitable for applications that require precise amplification of low-level signals.
One common application of chopper amplifiers is in precision analog-to-digital converters (ADCs) where maintaining accuracy is critical for high-resolution measurements. They are also used in various other precision instrumentation and sensor conditioning circuits.
It's worth noting that chopper amplifiers may introduce some additional noise and may not be suitable for applications requiring high-frequency operation due to the switching noise inherent in the chopping process. Engineers must carefully consider the trade-offs and requirements of their specific application before selecting a chopper amplifier or another type of op-amp.